Numerical investigation on the interaction between large-scale continuously stratified internal solitary wave and moving submersible

Internal solitary waves are a special type of non-linear ocean internal waves. Due to their high peak and deep valley, they can cause motion instability and loss of control of submersibles. This work investigates the interaction between large-scale continuously stratified internal solitary waves and an advancing submersible. Based on the fully nonlinear internal solitary wave theory, i.e. Dubriel-Jacobin-Long (DJL) equation, combined with Computational Fluid Dynamics (CFD) simulation, a three-dimensional wave tank is established using an initial flow field wave-making method. The effects of three key parameters, namely submergence depth, wave amplitude, and advancing speed, on the motion response and load characteristics are studied. The results show that the submergence depth has a great influence on the motion response of the submersible, especially for the submersible near the pycnocline. The wave amplitude and advancing speed mainly affect the load on the submersible and the duration of wave-body interaction. Due to the flow characteristics of internal solitary waves, the submersible will experience a bow moment. If the buoyancy suddenly decreases, the submersible will lose its “support” of fluid and sink rapidly. The mechanism of the “falling deep” phenomenon is finally revealed.